Oral Contraceptives Are Safe, Very Effective

UN Population Division, Department of Economic and Social Affairs, with support from the UN Population Fund (UNFPA)

Oral Contraceptives Are Safe, Very Effective


The electronic version of Network is being made available by the
Population Information Network (POPIN) of the United Nations
Population Division/DESIPA and Family Health International (FHI).


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Network, Vol. 16, No. 4, Summer 1996

Oral Contraceptives

Copyright 1996, Family Health International

Oral Contraceptives Are Safe, Very Effective

However, many women use pills incorrectly or discontinue them because of side effects or health concerns.

Oral contraceptives (OCs) are more than 99 percent effective in preventing pregnancy when used consistently and correctly, and they are safe for nearly all women. More than 70 million women use the pill worldwide, but incorrect use is common, thus lowering its annual typical effectiveness to about 92 percent.1/

OCs are among the most widely studied of all drugs. The benefits of using them far outweigh the potential risks for almost all women. However, oral contraceptives are not recommended for women at high risk of cardiovascular disease or women over 35 years old who are heavy smokers. Also, certain health problems may become worse with pill use.

“The pill is a very safe, highly effective product,” says Dr. Laneta Dorflinger, FHI director of clinical trials. “But we need to find ways to make sure it is used more effectively and continuously. Since failure during typical use is quite high and discontinuation rates are 50 percent or even higher in the first year of use, we have to determine how to help women do better.”

Side effects or health concerns are frequently mentioned as reasons for discontinuation, she says. For example, surveys in some countries where discontinuation rates are greater than 50 percent show about half of the discontinuations are due to side effects or health concerns: 24 percent of all pill users in the Dominican Republic stopped using them within the first year for these reasons, and 29 percent in Peru.2/ Changes in menstrual patterns are a frequent complaint, as are headaches, nausea and, less freqently, vomiting associated with pill use.

Allowing women to choose a contraceptive method from among a variety of good options is one way to encourage women to continue using any method, Dr. Dorflinger says. Counseling about potential side effects and providing good management of medical concerns can also improve use. For example, the quality of counseling affects how well prepared women will be to take the pill correctly, in addition to preparing them to handle side effects. In Zimbabwe, a survey among OC users who had missed their daily pill found only one woman in three who had taken the correct action after missing the pill, illustrating one area where more thorough counseling may be able to improve effectiveness.3/

Side effects and health

Because the hormones in the pill mimic pregnancy, the pill has some side effects that are similar to those associated with pregnancy. Nausea or vomiting may occur in the first few cycles of pill use, but are less common in subsequent cycles (taking the pill with food can minimize nausea). Women may also experience headaches, decreased libido, and depression or mood change. Other possible side effects include breast tenderness, acne, and dizziness.

The pill regulates a woman’s menstrual cycle, decreasing the amount of bleeding on the average by about 60 percent because of the reduced thickness of the endometrium. This effect may be beneficial for many women. For example, pill use can eliminate mid-cycle pain, which some women experience, and decreases menstrual cramps. Because of the decrease in bleeding, anemia may decrease.

A few women may experience amenorrhea, while others may have breakthrough bleeding between periods. Breakthrough bleeding, which can range from spotting to bleeding episodes, is generally not harmful to a woman’s health but may have some cultural or religious significance. Typically, side effects diminish within a few months after a woman begins OC use.

Since the pill was first introduced more than 30 years ago, there have been hundreds of major studies on risks and benefits. Long-term medical risks include the relationship of the pill to cancers and to cardiovascular disease (see related article, page xx). Most women can use the pill without safety concerns, according to medical eligibility criteria established by the World Health Organization (WHO).4/ It is safe for nonpregnant women past menarche and up to 40 years old (and usually safe after age 40), with or without children, of any weight including obese women. Postpartum women who are not breastfeeding may begin using the pill three weeks after giving birth, and breastfeeding women may do so after six months, although it is better to delay pill use until breastfeeding ends. Women can use the pill immediately postabortion. Women can use the pill if they have mild headaches, varicose veins, anemia, a history of diabetes during pregnancy, painful or irregular menstrual periods, malaria, benign breast disease, or thyroid disease, or if they carry viral hepatitis.

Some women should not use the pill under any circumstances, according to WHO. These include women who are pregnant, have a greatly increased risk of cardiovascular disease, are both over age 35 and smoke heavily (more than 20 cigarettes a day), and have certain preexisting conditions that could be worsened by OCs. These preexisting conditions include current breast cancer, benign liver tumors, liver cancer and active viral hepatitis. High risks for cardiovascular disease include blood pressure greater than 180/110 mm Hg, diabetes with vascular complications, complicated valvular heart disease, and a history of any of these conditions ( deep vein thrombosis, blood clotting in the lung, heart attack, stroke, or severe recurrent headaches with vision problems.

Under some medical conditions, the pill is not the best choice but is still acceptable if another method is not readily available or acceptable, or if a provider can monitor the woman. For example, healthy women over age 40 may generally use the pill, as can those younger than 35 who smoke. Those with sickle cell disease can use the pill but should be monitored due to an increased risk of thrombosis. Those with unexplained vaginal bleeding should usually not initiate pill use until the nature of the bleeding can be evaluated. If taking drugs that induce liver enzymes, women should usually not use the pill because the drugs are likely to reduce the effectiveness of OCs. These drugs include rifampicin and griseofulvin, which are antiboitics, and the following anticonvulsants: phenytoin, carbamezapine, barbiturates and primadone.

Without good counseling, a woman may not be able to distinguish between an expected side effect and a medical problem. A simple way to remember the danger signs of a medical problem is the English acronym ACHES: A for “abdominal” pain that is severe; C for severe “chest” pain, cough, shortness of breath; H for severe “headache,” dizziness, weakness or numbness; E for “eye” problems (vision loss or blurring) or speech problems; or S for “severe” leg pain (calf or thigh). The acronym can be modified to fit other languages.5/ These signs help identify a possible cardiovascular-related problem that may occur in the short term. The long-term risk of using the pill is very small for all women in developing countries compared to the risk of pregnancy.

There are medical benefits from pill use. Because of the pill’s excellent effectiveness in preventing pregnancy, women taking OCs have less chance of an ectopic pregnancy, where the fertilized egg develops outside the uterus, a life-threatening condition. Pill use also lowers the overall risk of symptomatic pelvic inflammatory disease (PID) by about 50 percent, because the thickened cervical mucus helps keep bacteria out, possibly the thinner endometrium provides less fertile ground for bacterial growth, and the decreased menstrual flow reduces the chance of pathogenic growth or movement of bacteria up the fallopian tubes.

False rumors about health problems can lead to discontinuation or incorrect use. “Some women think the pill is unnatural and may cause blocked tubes,” says Dr. Olivia McDonald, medical director of the National Family Planning Board in Jamaica, who is working with FHI and the Medical Association of Jamaica to provide contraceptive update seminars for Jamaican physicians, nurses and other health professionals. “So as not to keep this unnatural thing in their body, they don’t use the pill regularly,” thus lowering effectiveness.

OCs dissolve in the stomach and are rapidly absorbed into the bloodstream, just like other medicines. They do not build up in a woman’s body. Nor does a woman need a “rest period” from taking the pill. Taking a rest will only increase a woman’s chance of an unplanned pregnancy. Also, pills do not cause birth defects when a woman goes off the pill and gets pregnant.

Mechanism of Action

OCs work primarily by suppressing ovulation, while also affecting the cervical mucus and endometrium. OCs alter the natural production of estrogen and progestin in the body, suppressing the follicle stimulating hormone (FSH) and luteinizing hormone (LH). When taking the pill, the woman’s brain does not trigger the normal surge of FSH and LH needed for the follicle to mature and release an egg. The pill keeps the cervical mucus thick to prevent sperm penetration. It also causes the endometrium not to thicken as much as normal, thus making implantation unlikely in the rare event that fertilization takes place.

The cervical mucus action is particularly important for the progestin-only pill (POP), which does not cause the extent of ovulation suppression seen with combined pills (those containing boeth estrogen and progestin). The mucus thickens two to three hours fter a POP is taken, but remains thick for only about 24 hours unless another pill is taken. That is why the POP must be taken at about the same time, every 24 hours. If a POP is missed even by just three hours, a woman should use a back-up method if she has sexual intercourse.

The pill used today has changed substantially from the product that first went on the market in 1960. The original, “high-dose” pill had up to 150 micrograms ((g) of estrogen, compared to today’s “low-dose” pill of 35 (gs or less. The amount of progestin has also declined substantially. More recently, new progestins have been developed for low-dose OCs, which some call the “third generation” pills.

The new formulations were designed to reduce safety risks and side effects. The low-dose pill, with much less estrogen, for example, has less impact on blood pressure, blood clots, carbohydrate metabolism and other factors for cardiovascular-related diseases. Lower doses of estrogen have been associated with less nausea, vomiting and headaches. Some researchers think the third generation pills with the new progestins also reduce side effects, for example, reducing rates of amenorrhea. Others feel the literature is not clear.6/

Studies have not found clear connections between different pill formulations, changes in side effects and resulting discontinuation rates. A multicenter clinical trial involving almost 1,700 women assessed the relationship between side effects and discontinuation rates, comparing women using a 50 (g and 35 (g pill. The low-dose users reported significantly more intermenstrual bleeding, while those taking high doses reported more breast discomfort. “There were no significant differences between the groups for gross cumulative life table discontinuation rates,” reported Vivian McLaurin and Randy Dunson of FHI, who coordinated the study.7/

The most common pill form is monophasic, where the hormone levels are constant throughout the 21 days of active pills. Combined OCs also exist in biphasic and triphasic forms, where the ratio of estrogen and progestin varies among the active pills, twice during the cycle for the biphasic and three times for the triphasic. This variation allows the pill to mimic a woman’s natural hormonal cycle more closely in the hopes of reducing side effects, although research has not generally shown this to be true. Most pills used in developing countries are monophasic.

Who can take the pill?

The pill is ideally suited for women who want to delay pregnancy and space children. Fertility almost always returns soon after a woman quits taking the pill. The pill is a good choice for those who want to control their own contraception. A woman can use the pill without a partner’s knowledge, if desired. Women must arrange for resupply on a regular basis and be conscientious about taking the pill throughout the cycle.

According to WHO, breastfeeding women who want to take the pill should use the progestin-only pill, beginning no sooner than six weeks after delivery if fully breastfeeding. In general, combined oral contraceptives ae not recommended for breastfeeding mothers because estrogen diminishes the amount of breastmilk. Although combined OCs may be used six weeks postpartum if lactation is well-established and other options are not available or acceptable, ideally breastfeeding women should not use combined pills until at least six months postpartum.

A U.S. Agency for International Development panel of experts from several collaborating organizations, including FHI, has identified procedures health providers need to follow in order to distribute the pill safely.8/ The only essential procedure is good counseling on efficacy, side effects, changes in menstrual patterns, correct use, problems that require seeing a health-care provider, and STD protection. Distribution does not need to be confined to clinics. Community-based distribution systems can follow these procedures, making the pill more easily accessible.

Sometimes unnecessary procedures are required before prescribing the pill. Providers in many countries require that a woman is having her menstrual period in order to get a prescription for the pill, to ensure that she is not pregnant. This step is medically unnecessary since screening at any time can reasonably assure that a woman is not pregnant. An unplanned pregnancy may result if a woman must wait several weeks before beginning the pill. Providers can be reasonably sure that a woman is not pregnant if she has not had pregnancy symptoms, such as absent or altered menses, and she is within the first seven days of onset of normal menses, or has not had recent sexual activity, or has been correctly and consistently using a reliable method.

Some procedures, such as breast exams and blood pressure tests, may be indicated for some women before beginning OCs. However, pelvic exams and screening for cervical cancer and STDs should not be routinely required for OC use, but may be appropriate for good preventive health. Routine lab tests for cholesterol and other functions have no relationship to safe pill use and should not be required before pill use.

In Senegal, the expense of lab tests was compared with possible safety risks Before 1990, full laboratory tests were routinely given to women before they could receive the pill. A prospective study of 410 women found that the cost to the woman of the required laboratory tests ranged from U.S. $55 to $216, as much as five times the monthly per capita income in Senegal. Of the 410 women, 20 were found to have possible health problems upon initial testing. Nine of the 20 returned for retesting. Of those, only one was confirmed as having a problem that meant she should not take the pill. The study and a subsequent meeting led to a change in policy in Senegal, with the government no longer requiring laboratory testing before pills can be prescribed. “However, many doctors and midwives have resisted the recommendation, and laboratory testing prior to prescriptions of the pill is still widespread in urban Senegal,” reported John Stanback of FHI, the study coordinator, and his colleagues.9/

STD/HIV considerations

Oral contraceptives do not protect against sexually transmitted diseases (STDs), including HIV. If a woman is at risk of becoming infected with an STD, she should use condoms consistently regardless of her OC use.

“Pills are designed to prevent pregnancy, and they do it well,” says Dr. David Grimes, chief of obstetrics and gynecology at San Francisco General Hospital, University of California at San Francisco, who has published reviews on pill safety issues. “Pills are not designed to protect against STDs. I have a coffee pot that works very well, but it can’t answer the phone. For the phone, I had to buy an answering machine. The coffee pot was never intended to answer the phone. Nor was the pill designed to protect against STDs.”

Research is not clear on the possible relationship of OC use to the transmission of STDs. Women using the pill are more likely to have chlamydial cervicitis, an STD. Transmission of HIV can be more likely if a person has an STD, including chlamydial infection. However, research has not shown whether there is an association between pill use and risk of HIV transmission.

A recent animal study has raised concerns about a possible increased risk. In the study, rhesus monkeys were given doses of the hormone progesterone, the body’s natural form of progestin. The monkeys were found to be more likely to become infected after exposure to simian immune deficiency virus (SIV), a virus similar to HIV in humans. However, data from human studies are inconsistent. More research is needed to assess the implications of this study among humans (see related article on page 18).

( William R. Finger


1. Moreno L, Goldman N. Contraceptive failure rates in developing countries: Evidence from Demographic and Health Surveys. Int Fam Plann Perspect 1991; 17(2): 44-49.

2. Dominican Republic: Demographic and Health Survey 1991. Peru: Demographic and Health Survey 1991-1992. Calverton, MD: Macro International Inc., 1992.

3. Zimbabwe: Demographic and Health Survey 1994. Calverton, MD: Macro International Inc, 1995.

4. Improving Access to Quality Care in Family Planning: Medical Eligibility Criteria for Contraceptive Use. Geneva: World Health Organization, 1996.

5. Church CA, Rinehart W. Counseling clients about the pill. Popul Rep 1990; Series A(8): 11.

6. Hatcher RA, Trussell J, Stewart F, et al. Contraceptive Technology Sixteenth Revised Edition. New York: Irvington Publishers, Inc., 1994.

7. McLaurin VL, Dunson TR. A comparative study of 35 mcg and 50 mcg combined oral contraceptives: results from a multicenter clinical trial. Contraception 1991; 44(5): 489-503.

8. Curtis KM, Bright PL, eds. Recommendations for Updating Selected Practices in Contraceptive Use: Results of a Technical Meeting, Volume 1. Chapel Hill: Technical Guidance Working Group, U.S. Agency for International Development, 1994.

9. Stanback J, Smith JB, Janowitz B, et al. Safe provision of oral contraceptives: The effectiveness of systematic laboratory testing in Senegal. Int Fam Plann Perspect 1994; 20(4): 147-49.

Copyright 1996, Family Health International. Any part of this text may be copied, reproduced, distributed or adapted without permission from the authors or publisher, provided that the recipient of this text may not copy, reproduce, distribute or adapt this text for commercial gain, and provided further that Family Health International is credited as the source of such information on all copies, reproductions, distributions and adaptations of this text.

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